Robotics and Automation Systems and Interfaces (RAS)

Robotics and Automation Systems and Interfaces (RAS)

1.1 Overview

Due to the harsh conditions on the Martian surface and the many time consuming and monotonous task, robotics and automation will play a vital role in habitat operations. The robotics and automation subsystem is responsible for designing the automated systems and interfaces that are outside of the scope of other subsystems. RAS is also responsible for designing the interfaces between all robotics systems and the habitat, except for the LPR, which is also covered by EVAS. The habitats robotic systems have a major role in the development of infrastructure elements of the habitat and habitat operations, including site analysis, habitat assembly, instrument deployment, and scientific investigation.

The level 2 requirements for RAS are given below:

G1. Deploy scientific instruments used for initial analysis and monitoring of mars.

G2. Deploy Infrastructure (nuclear power station, antennas, solar arrays, etc.).

G3. Provide method of sample acquisition.

G4. Provide method for Infrastructure inspection and maintenance.

G5. Provide for construction and assembly of site and structures (site preparation, drilling, excavation).

G6. Provide local transportation for EVA activity.

G7. Robotics shall operate through entire mission duration.

G8. Robotics shall support control and communication (telerobotic or fully autonomous based on mission).

G9. Diagnosis and maintenance of robotics shall be automated (repair if possible).

G10. Robotics shall meet all fault tolerances and safety standards.

G11. Robotics shall meet all size and weight restrictions.

G12. Robotics shall provide for movement (Auto, teleauto).

G13. Robotics shall support payload operations.

G14. Equipment shall meet thermal-loading tolerances.

G15. Deploy and operate various mechanisms on habitat

G16. Robotics will support deployment and assembly of power plants.

G17. Automate time consuming and monotonous task.

G18. Mass for Robotics and Automation is included in Structures and CCC.

Figure # - Input/output diagram for RAS.

The input/output diagram for RAS, figure #, is a relatively simple one. Most of the subsystems interaction is with C3, these communications allow for control of the automated systems. There is also an exchange of audio data with EVAS, so that the rovers can communicate with crewmembers out on EVA. The last connection for RAS is to the Thermal and Power subsystems, for the removal of heat and a power transfer for recharging of the rovers and the automated systems.

1.2 Design and Assumptions

The main robotic systems that will be required for habitat operations are three different types of rovers, including: the small scientific rover, the local unpressurized rover, and the large pressurized rover. It should be noted however, that the RAS subsystem was not responsible for the design of these systems due the fact that the scope of the project was the design of the habitat and these system fall outside of that. So what will be covered are the requirements for the rovers driven by habitat operations and the interfaces between the rovers and the habitat.

1.2.1 Small Scientific Rover

Two small scientific rovers will be used mainly for exploration. These rovers will be autonomous a majority of the time, but will have the capabilities to perform tele-robotic operations, with the controller stationed in a shirtsleeve environment. Also, the rover will be capable of self- recharging through solar panels.

Figure # - MER rover, close to the expected rovers that will be used.

This type of rover will be required to: deploy scientific instruments, collect and return samples from the Martian surface, determine safe routes for crew travel, and act as a communications relay in contingency situations. The interface between these rovers and the habitat will be minimal. Only data will be transferred to and from the habitat. The data will consist of telemetry, audio and video, and any other necessary data from the rover’s scientific instruments.

1.2.2 Local Unpressurized Rover

The cargo carrier will also be bringing one local unpressurized rover (LUR). This rover will be required to provide local transport, around 100 km from the habitat, for the EVA crews and EVA tools. The LUR will also be required to operate for 10 hours, with the charge/discharge cycle being under one day. This type of rover will have two interfaces with the habitat, exchanging both power and data. The power will be transferred via a direct connection, with the outlet positioned on the outside of the habitat, and the inlet connection placed on the outside of the rover. The rover will also be sending and receiving audio and relaying telemetry information to and from the habitat.

Figure # - Conceptual local unpressurized rover.

1.2.3 Large Pressurized Rover

The final rover to be covered is the Large Pressurized Rover (LPR). Two LPRs will be brought to the surface on the first cargo carrier. It should be noted that any EVA aspects of this rover are discussed in the EVAS section of this paper. The LPRs will have a few critical responsibilities that must be carried out before the first crew arrives, including: site preparation, moving, deploying, and inspecting the habitat’s infrastructure, and connection and inspection of the ISRU and power plant. This will be done with 2 mechanical arms and a powerful locomotive system. With all of these task being performed with out the assistance of EVA crews, the LPR will be able to be fully automated, but will also have tele-robotic capabilities. The LPR will interface with the habitat directly, though this is mostly for EVAS concerns. Other interfaces will involve the transfer of data, including telemetry, audio, and video.

Figure # - conceptual mechanical arm for the LPR.

1.2.4 Small Rover Sizing

The small rover’s power requirements were sized using from the Mars Exploration Rover using a power to weight ratio. The MER uses .1 kW and weighs 180 kg and the small rover is sized at 440 kg from the . This results in .244 kW of power for the small rover. A 25% safety factor was then added to this for a total of .3 kW.

1.2.5 Medium Rover Sizing

The medium rover’s power requirements were calculated using the same method except with the large pressurized rover as a reference. The large rover was allocated 10 kW from the DRM and weighs 15.5 metric tons. Using these numbers, the power for the medium rover was calculated to be 2.8 kW. However, a certain percentage of this power is used for life support systems on the pressurized rover and does not need to be incorporated into the power requirements for the medium rover, which does not need to support any life support systems. In order to account for this, the power requirement was reduced by 30%. A 25% safety factor is still factored in though for a total of 2.5 kW.

1.2.6 Large Rover and Arm

The power requirements and the weight of the large pressurized rover were both specified in the DRM at 15.5 metric tons and a 10 kW power requirement. A significant portion of this power will be used to power the two arms on this rover. The exact power requirements on these arms are difficult to size due to tasks needing to be specified. Existing arms such as the ones on the ISS use 2000 W at peak power but also operate in a zero g environment. However this arm is also able to move the entire orbiter at slow rates. It is likely that the arms on the pressurized rover will use similar power, based on the total power of the large rover. An initial estimate of the power for these arms is 2.5 kW, based on Mars gravity and max loads of moving the airlocks and reorienting the habitat.

1.2.7 Sizing of Leveling and Radiator Deployment Systems

For the tasks of initial leveling of the habitat and radiator deployment, research was conducted on existing commercial off the shelf technology for mass, power and volume estimates. The initial leveling of the habitat will require 12 linear actuators with two on each of the six legs for redundancy purposes. The actuators have 720 mm of travel and can produce a total force of 50000 N. Their mass is 60 kg each for a total mass of 720 and they use 35 watts each. Any increase in the amount of travel will result in a slight increase in mass. For deployment of the radiator panels, 8 total actuators will be used with 2 on each of the panels. The actuators have 1 m of travel and produce 7500 N of force. Their mass is 9 kg each for a total mass of 72 kg and each uses 5 watts of power.

1.2.8 Automated Systems

The following are examples of items that will also be automated on the habitat. Similar actuators, motors, and servos will be incorporated and sized based on the size of the task.

•  Automated doors in case of depressurization

•  Deployment of communications hardware

•  External monitoring equipment

•  Deployment of radiator panels

•  Leveling of habitat

•  Compaction of waste

•  Deploy airlock

•  Connection of power plant to habitat and ISRU

•  Connect ISRU to habitat

•  Inspection and necessary maintenance of habitat and ISRU

•  Assumptions – small automated processes such as gas regulation will be taken care of by their subsystem

1.3 Verification of Requirements

1.3.1  Requirements Verification

All of the following requirements that were specified in the original requirements document for the robotics and automation subsystem were met with the exceptions explained later. These include requirements that the small rover will be used to meet, such as: deploy scientific instruments, provide method of sample acquisition, determine safe routs for crew travel, and be used as a communications relay in contingency situations. The requirements that the large rover will be used to meet are: site preparation, deploy move and reorient infrastructure, inspect infrastructure, shall support EVA activity, will connect directly to habitat, and connect power plant ISRU and habitat to each other. The requirements that the medium rover will meet are: must provide for local transportation, must be recharged via external male/female cable, charge/discharge cycle must be less than one day. There are also some general requirements that all the rovers must meet, these include: robotics shall operate through entire mission duration, robotics shall support control and communication (telerobotic or fully autonomous based on mission), robotics shall meet all fault tolerances and safety standards, robotics shall meet all size and weight restrictions, and robotics shall support payload operations. There were several requirements for the automation systems that were met these include: equipment shall meet thermal loading tolerances, shall support power requirements, must deploy and operate various mechanisms on the habitat, Time consuming and monotonous activities will be automated.

The requirements that were not explicitly met were the ones that involved the design of the rovers. Since the design of the rovers was not included in the project and only the interface of the rovers was designed, these requirements were assumed to have been met by the rover design teams. Another requirement that was not completely met was the requirement to automate all monotonous tasks. This was not met because at this stage in the design all of those tasks are not known.

1.3.2  Why Use Robotics

With everything that can go wrong with robotics and the complexity involved there may be a point where a human EVA would be a better alternative. In this situation there are several areas that should be considered. The first of these is safety of the crew. When an EVA is done the safety of the crew is at a much larger risk than it would be if the task was done by a robot, a robot is much easier to fix than a human being. The second consideration is wear and tear on suits. The more EVA’s are done the more wear the suit is subjected too. This has two repercussions the first is that more time and resources must be allocated to repairing the suits. The second is the higher risk of a suit failing outside due to the higher amount of use the suits will be seeing. One last consideration is that robots are good for repetitive activities especially in a hazardous environment. EVA’s for repetitive tasks are more dangerous due to the fact the astronauts get accustomed to the task and will start cutting corners and getting sloppy with the task. This increases the danger of the task and puts the astronaut at greater risk.

1.3.3  Future Considerations

There are several areas that need to be addressed for the future devolvement of this project. The first of these is that more complete design specifications for the rovers are needed. The hatch for the large rover needs to be designed which will require dimensions from the large rover design teams. Efficiencies for the recharging rate on the medium rover needs to be specified to the recharge time can be better calculated. Data rates need to be specified for all three rovers so that antennas can be sized and power requirements can be determined.

As the project progresses each of the subsystems will have a better idea of what tasks they need automated and if they will be taking care of them or if they should be handled by robotics and automation. Further specifications and definitions of these activities will also allow for specific hardware selections.

The orientation of the habitat has raised several questions as to how it will be accomplished. There are several ideas to this the first is that it will land vertically and then be lowered onto its side. There are several problems with this. The first is that in order to do this a level of stability must be added in that might as well be used to keep the habitat vertical in the first place. The second is the level of complexity of lowering it once it has landed. This procedure would be very hazardous to the habitat and could be disastrous. Another idea is that it could land on its side. This would mean that once it is in the atmosphere and the heat shield has fallen off parachutes would have to rotate it to its side. However parachutes are not enough to land by themselves. The habitat will have to have some other way of slowing its decent, this could be several rockets that would fire, or possibly inflatable balls so it could bounce once it landed like the MER missions.